Tumor necrosis factor alpha (TNFα) is a cytokine produced by monocytes and macrophages. It is found in synovial cells and macrophages in the tissues. It can be produced by many other cell types such as CD4+ lymphocytes, NK cells, neutrophils, mast cells, eosinophils, and neurons.
Apremilast is a TNFα inhibitor and marketed in United States under the brand name OTEZLA®. Apremilast is indicated for the treatment psoriatic arthritis. It is also used to treat moderate to severe plaque psoriasis in certain patients. The chemical structure of apremilast described in compound 1 as below.

Apremilast is a white to pale yellow powder in appearance. The drug substance is the S-enantiomer of N-[2-[1-(3-ethoxy-4-methoxy-phenyl)-2-(methylsulfonyl) ethyl]-2,3-dihydro-1,3-dioxo-1H-isoindol-4-yl] acetamide.
The U.S. Pat. No. 8,242,310 describes a process for preparation of amine compound of formula (I) by reacting benzonitrile compound of formula (IV) with Lithiumdimethylsulfone compound. The present invention also provides the process for preparation of intermediate of formula A and its conversion to apremilast in subsequent steps.
The U.S. Pat. No. 7,427,638 describes S-enantiomer of apremilast as a product and process for preparation thereof.
The U.S. Pat. Nos. 7,893,101 and 8,093,283 discloses a Form A, Form B, Form C, Form D, Form E, Form F and Form G of apremilast and process for preparation thereof.